Revert "drm/i915: Declare the swizzling unknown for L-shaped configurations"

This reverts commit 19ee835c.

It breaks existing old userspace which doesn't handle UNKNOWN
swizzling correct. Yes UNKNOWN was a thing back in 2009 and probably
still is on some other platforms, but it still pretty clearly broke
the testers machine. If we want this we need to extend the ioctl with
new paramters that only new userspace looks at.

Cc: Harald Arnesen <harald@skogtun.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reported-by: Harald Arnesen <harald@skogtun.org>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>